HP 3455A reference bargain on ebay

[codeboy2k]

I'm browsing eBay and I find a guy selling two six HP 3455A references , but he thinks they are crystal oscillators (I guess they look the same to him )

These are HP part numbers 11177B.

• The HP3455A was a 6 digit DVM introduced around 1977/78 I think.
• The reference is a 10 volt reference, well aged by now, and thus will be stable as hell, probably down to 1 ppm per year.
• The core of the reference is a heated zener in a can, HP part 1902-0926, that is very similar to the LM399 (maybe even the same part? Vincent, do you know? )
• The 3455A is described here in the HP Journal: http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1977-02.pdf

The reference board also contains about 4 or 5  0.01% 1 ppm divider resistors in hermetic cans.  Those alone are worth $30 - $50 each if you try to buy them new.

He's asking $49.00 + shipping, but he's also taking best offers, so if you're looking to build a 10V bench reference then you might be able to get a stable, 10V, heated reference for much less than the $129.00 + shipping that the 3458A references are going for (of course the 3458A refs are also LTZ1000's, I know). It's certainly going to be better than the many plastic chip references that are available from $49 - $100+, that aren't going to be nearly as stable as these HP3455A references will be.

Here is the links:

http://www.ebay.com/itm/HP-11177B-00252-CRYSTAL-OSCILLATOR/161612819510
http://www.ebay.com/itm/HP-11177B-01723-CRYSTAL-OSCILLATOR/151599716338
http://www.ebay.com/itm/HP-11177A-12883-CRYSTAL-OSCILLATOR/151599739448
http://www.ebay.com/itm/HP-11177A-11236-CRYSTAL-OSCILLATOR/151599699094
http://www.ebay.com/itm/HP-11177A-12933-CRYSTAL-OSCILLATOR/151599686056
http://www.ebay.com/itm/HP-11177A-304-11177-69501-CRYSTAL-OSCILLATOR/151599695954

Note that there is some A and B models here.. the picture below is the B model.  According to the schematic, the A model has a zener in a can with a heater, and the B model has a temperature compensated zener in a can with a heater, AND the heater current is in a feedback loop with the diode output voltage.  The A models, while still good, are not going to be as stable as the B models.

Why am I posting here, instead of buying these up myself?? Because I'm quite literally broke, and looking for work. I need to save all I can, and as much as I'd love to have this for myself, I don't need it. But I would love to see some EEVblog forum user do something worthwhile with it at a bargain price.

(PS: I am not the seller, the seller is in Texas but will ship worldwide.  I am in Canada.  Still, you buy at your own risk, since there is no indication that these even work still !)

Here's some pics of the same reference from a random blogger:
http://www.simonsdialogs.com/?p=1209

[kmel]

Thank you for the tip! Got one for $35.

[codeboy2k]

nice.  keep us posted about it when you get it.

[Vgkid]

GREAT!!!!!!! Now everyone nows(they were on my secret watch list)

[TiN]

Better be quick. Got one for 40 

[max666]

Thanks for the tip, really big of you!

[codeboy2k]

Good to see some people scooping these up.  I'd like to see TiN's review

My wife will kill me if I spend the $40 on something that's not absolutely necessary right now.

[TiN]

Was there, know it. Will review it and compare to LTZ & VPG stuff I have.

[codeboy2k]

GREAT!!!!!!! Now everyone nows(they were on my secret watch list)

.. and did you get one?  they are all sold now.. the seller must be wondering why there was a flurry of activity

[codeboy2k]

Was there, know it. Will review it and compare to LTZ & VPG stuff I have.

Yes, that's what I thought you might do I'm curious too.

I will have my time to buy play toys again in the future

[Vgkid]

Nah, I'm to cheap. Not like an need anything voltage related, have a semi-recently cal'd 3456a, 34401(both agree within 2ppm at 10v), mv106(needs to be adjusted, 40ppm out between both meters), broken Solartron 7065(I'll chuck it on ebay, tired of messing with it, it works.)

[barnacle2k]

i grabbed the last two, thanks for the head up. 

Relevant thread:
https://www.eevblog.com/forum/testgear/hp-3455a-teardown/

[codeboy2k]

Nice, good to see you guys pick them up, let us know what you do with them

It looks like a really nice reference, especially with those 0.01%, 1 ppm  resistors on-board.  Those can be used as a nice resistance check on a DMM.

Also, that 16-pin ceramic is actually a precision resistor network, although I don't know the specs. Anyone?  The schematic that I have seen online is garbage, totally unreadable, like it was scanned at  just 72 dpi resolution or something.   Just awful.  So if anyone has a better copy of the schematic, or can scan it, post it here please.

That ebay seller is on my watch list, he's got some very reasonable prices.

[TiN]

Rehosted manual here already. Beware, 56 megs
Page 227. Not sure if its for A-version or B-version, I'm not that familiar with HP gear.
I got this REF mainly for resistors, but will test how stable it is against K2002 and KX LTZ1000 references.

[codeboy2k]

That manual is really clear !  Thanks TiN.

Both the A and B models are there.

The A model is on page 227 and is marked A11 in the upper left corner.  The B model is on page 226 marked A20.

The B model has the extra opamp, U3, that servos the heater current.

[barnacle2k]

I intend to use them as 10V and resistance standards.

From that service manual it seems the A20 version uses a custom temp compensated zener with oven, while the A11 version uses a LM399.
The A20 seems to be the later version.
That custom zener propably has less drift and noise then the LM399.
In regards to A vs. B revision of a specific version it seems the B version is just a selected version A. (tighter tolerance / more burn in maybe?)
Note that there are A and B revisions of 03455-66511 and 03455-66520 on page 224, and they do not differ in components.

So all fingers crossed for that rare custom zener thingy, will it beat the LTZ1000? 
It can be seen on the picture in the first post the left to99 can in the front, that is definitely not a LM399!

Edit:
Found a picture of a A11 reference assembly with the classic LM399:

[codeboy2k]

I intend to use them as 10V and resistance standards.

Yep. That's what I would have used it for too.

As you said, my first post has a picture of the B version with the temperature compensated zener and oven (in a feedback loop). It's the HP part 1902-0926.  Oddly it's not wrapped up like the LM399 is. Retro-fitting a simple press-on styrofoam cover might help it stabilize even more.

[TiN]

Goodies have arrived...

Thanks.